西藏高原羊易地热田深部构造的近震转换波研究

首次利用三分量数字地震仪在西藏羊易地热田区记录到近震转换波,并用于研究深部构造取得了结果.查明了测区基底构造的基本特征,发现热田区发育了NNW和NEE向一系列断裂,其延深可达6-9km,不同方向断裂的交汇对热田有控制作用.在热田内基底形成一近NS向断块状局部隆起.经过热田深部传播的近震转换波的频谱主频和振幅比均有明显降低,这些特征显示热田深部可能有局部熔融的岩脉沿深断裂活动.表明在热田区的微震观测中同时利用近震转换震相研究深部构造是可行的.

INVESTIGATION OF THE DEEP STRUCTURES IN YANG YI GEOTHERMAL FIELD IN TIBET PLATEAU BY USING CONVERTED WAVES OF NEAR EARTHQUAKES

Some significant results have been obtained for the first time in studing deep structures of Yang Yi geothermal field in Tibet plateau by using try method of converted waves of near earthquakes with three-components digital seism c recorders. The basic structure features of the basement in the studied region have been revealed. It is found out that a series of NNW(near NS) and NEE (near EW) faults going down to the depth of 6-9 km are located and intersected in the geothermal field. There is a local uplifted fault-block with near N-S trend in the basement of the geothermal field. Propogating through the geothermal field, the dominant frequence of the spectrum and the amplitude ratio of the converted waves become lower. It indicates that the partially melted magma and het water steam may have been intruded into the beneath of the geothermal field along the faults.It is suggested that in the investigation of geothermal fields simultaneously analyse and interpretation of P, S waves and PS converted phases of the near earthquakes is available.